Untitled

ε-Fe2O3: An Advanced Nanomaterial Exhibiting Giant Coercive Field, Millimeter-Wave Ferromagnetic Resonance, and Magnetoelectric Coupling

“…In the case of spherical ε-Fe 2 O 3 nanoparticles, their diameter ranges from ∼10 nm to > 200 nm, , whereas nanorods (nanowires) are typically ∼20 nm to 2 μm long and ∼10−50 nm wide (see Figure ). ,, The systems that are comprised of either ε-Fe 2 O 3 nanospheres or ε-Fe 2 O 3 nanorods (nanowires) generally exhibit a size distribution character that is presumably governed by the particular synthesis method and its conditions and/or, in some cases, by the particle size distribution of the precursor (e.g., in methods based on thermal transformations of Fe 2 O 3 polymorphs and Fe 3 O 4 ). The sphere morphologies of ε-Fe 2 O 3 can be obtained via the thermal decompositions of suitable iron-containing precursors , or their oxidation advanced by high-energy deposition techniques, including electric discharge, gamma irradiation, laser-assisted pyrolysis, and sol−gel methods, followed by heat treatments at a certain temperature and for a definite time. ,,, On the other hand, nanorods and nanowires of ε-Fe 2 O 3 can be synthesized employing combination of the reverse-micelle and sol−gel methods (where Fe(NO 3 ) 3 is used as a precursor), microemulsion/sol−gel method (where Fe(NO 3 ) 3 is used as a precursor), ,, and/or by vapor−liquid−solid mechanisms assisted by pulsed laser deposition (where Fe 3 O 4 is used as a precursor). , Preparation techniques based on thermal decompositions and oxidation involve heat treatment of Fe-bearing precursors such as a mixture of Fe 2 O 3 polymorphs, Fe 3 O 4 , basic ferric salts, and other precipitates derived from the ferric iron salts in basic solutions. Concerning high-energy deposition synthetic methods, they promote the oxidation of vaporized iron, iron(II) formate, and an Fe(CO) 5 −N 2 O gas mixture.…”

“…40,43,45 The systems that are comprised of either ε-Fe 2 O 3 nanospheres or ε-Fe 2 O 3 nanorods (nanowires) generally exhibit a size distribution character that is presumably governed by the particular synthesis method and its conditions and/or, in some cases, by the particle size distribution of the precursor (e.g., in methods based on thermal transformations of Fe 2 O 3 polymorphs and Fe 3 O 4 ). The sphere morphologies of ε-Fe 2 O 3 can be obtained via the thermal decompositions of suitable iron-containing precursors 26,38 or their oxidation advanced by high-energy deposition techniques, including electric discharge, 30 gamma irradiation, 74 laser-assisted pyrolysis, 75 and sol-gel methods, followed by heat treatments at a certain temperature and for a definite time. 28,39,46,76 On the other hand, nanorods and nanowires of ε-Fe 2 O 3 can be synthesized employing combination of the reverse-micelle and sol-gel methods (where Fe(NO 3 ) 3 is used as a precursor), 45 microemulsion/sol-gel method (where Fe(NO 3 ) 3 is used as a precursor), 16,40,51 and/or by vapor-liquid-solid mechanisms assisted by pulsed laser deposition (where Fe 3 O 4 is used as a precursor).…”

Optimized Synthesis of the Elusive ε-Fe2O3 Phase via Sol−Gel Chemistry

“…In the thermal decomposition experiments, Fe 2 O 3 mixed oxides, basic ferric salts, , and other precipitates, obtained from ferric iron salts in basic solutions, were thermally treated. Concerning high-energy deposition syntheses, techniques such as electric discharge, gamma irradiation, or laser-assisted pyrolysis were used to oxidize vaporized Fe, Fe(II) formate, and an Fe(CO) 5 −N 2 O gas mixture, respectively. More recently, the sol−gel approach has opened new scenarios for the synthesis of the ε-Fe 2 O 3 polymorph. − Silicon alkoxides with Fe nitrate precursors are an effective way to synthesize ε-Fe 2 O 3 , but typically they yield mixtures of ε-Fe 2 O 3 plus α-Fe 2 O 3 and/or γ-Fe 2 O 3 .…”